The present invention relates to optical sights for weapons, measurement instruments, geological surveying instruments, or the like, and more specifically to optical sights with wide range of observation distances. In particular, the invention relates to a universal optical sight that has a telescopic tube for long-distance viewing or shooting combined with an illuminated-reticle sight for short-distance viewing or shooting.
In the last few years the optical sighting technique for firearms and measurement field is characterized by rapid development and sophistication. It is understood that an optical sight would be ideal for use, e.g., on firearms or other weapons, if it could be used for shooting at close as well as at distant targets without disassembling or time-consuming refocusing of optical elements of the sight.
Among a great variety of various telescopic optical sights known in the art, one such sight attachable to a firearm is described, e.g., in U.S. Pat. No. 5,924,234 issued to G. Bindon, et al. in 1999. This is a typical telescopic sight having an objective lens assembly, an eyepiece lens assembly, and an illuminated reticle imposed onto the vision view of the optical sight. If this sight has been focused for aiming at a remote target, but the shooter has to hit a close target, which appeared in his/her field of vision for a very short period of time, the close target can disappear sooner than the shooter would be able to refocus the optical sight. Furthermore, the range of shooting distances inherent in optical telescopic sights is within the limits of from about 30 m to several hundred meters or several kilometers. In general, an optical telescopic sight is not suitable for hitting targets at distances closer than 30 m. Moreover, the use of telescopic sights at short shooting distances is extremely inconvenient because the telescopic optics has a limited aperture, so that only a narrow scene can be observed in the optical sights focused to short distances.
Quite often however, such circumstances are usually accompanied by other difficulties as well. For example, one such circumstance may be a battlefield. Under battlefield conditions it is highly advantageous to have an optical sight that has both a wide field of view and a narrow field of view available to the user. For example, it is quite advantageous for a gunner to be able to select a target over a wide range of distances. Hence, an optical sight having one set of optical elements having a wide field of view, for relatively closer range targets and a second set of optical elements which, when positioned in the optical path of the first set of optical elements, presents a narrow field of view, for relatively distant targets, provides a gunner with the ability to select, track and/or attack targets over a large tactical battlefield.
An attempt to solve the above problem is described in U.S. Pat. No. 5,548,442 issued to G. Devenyi in 1996 and in U.S. Pat. No. 5,691,842 issued to the same inventor in 1997. These patents describe an optical assembly that includes a first plurality of optical elements providing the viewer with a first field of view and a second plurality of optical elements that, when moved into the optical path of the sight, provides the viewer with a second field of view. This is achieved by providing the sight with an optical lens subassembly installed rotatingly inside the sight housing with the axis of rotation transverse to the optical axis of the sight. In one position of the optical lens subassembly the optical axis of this subassembly coincides with the optical axis of the sight and the lenses of the subassembly are included into the optical scheme. This position corresponds to one field of view. When the optical lens subassembly is turned by 90xc2x0 from the first position to the second position, the lenses of the subassembly are removed from the optical scheme, and the light beams freely pass through the windows provided in the sub-assembly configuration. U.S. Pat. No. 6,226,880 issued in 2001 to R. Pitre describes a quick focusing firearm scope, which includes an elongated tubular scope housing mounted to the upper surface of the firearm barrel. A focusing gear is provided in place of the conventional rotating focusing ring found on conventional scopes. Mounted adjacent to and engaging the focusing gear is a drive gear having a cable attached thereto. The opposing end of the cable extends through a support member that is mounted to the firearm trigger guard. Pivotally attached to the support member is a trigger member having an arcuate gear attached to the upper end thereof that engages a rotary gear on the cable. The lower end of the trigger member includes a loop that receives a shooter""s trigger finger. Accordingly, a shooter may quickly focus the scope by pivoting the trigger member with the index finger. This allows a shooter to quickly focus the scope without removing his or her hand from the trigger.
Nevertheless, the device of U.S. Pat. No. 6,226,880 does not solve the problem of switching from distant telescopic sight to a close sight inherent in conventional non-optical rifle sights.
Optical sights intended only for short-distance shooting are known. One such device is described, e.g., in U.S. patent application Ser. No. 09/749982 filed in 2000 by the same applicant as the present patent application. This patent application describes an optical sight for a photocamera or for an aiming device of a firearm, which comprises a combination of a light emitting diode (LED) with a plurality of reticle patterns applied onto the surface of the LED and selectively illuminated by connecting various portions of the reticle pattern to the source of electric power supply. Switching from one pattern to another is carried out electrically without the use of moving the reticles or reticle images. This ensures high accuracy in positioning of reticle elements with regard to each other, e.g., with regard to the front sight center of the partially transparent mirror, and hence, with regard to the ballistic trajectory of the bullet.
More specifically, the aforementioned LED is installed on a mounting plate in the proximal part of the sight and is positioned offset from the optical axis of the sight. The distal part of the mounting plate supports a concave partially transparent mirror through which the viewer can see a target. A special mirror coating passes about 95% of the light and reflects about 5% of the light incident on the mirror. The LED is spaced from the coating of the mirror at a distance equal to half the radius of the curvature on the concave surface of the mirror. The aforementioned reflected part of the light has a shape of a collimated beam. The sight is further provided with an eyepiece, and the mirror coating is arranged so that the beam reflected from the mirror surface is aligned with the axis of the eyepiece. If the beam carries an image (reticle), this image will be localized on the retina of the viewer""s eye and will be seen as if it is located in the infinity. The reticle image will be imposed onto the image of a target seen through the partially transparent mirror.
The sight of the aforementioned type is intended for aiming at objects located at short distances, which normally do not exceed 100 meter. The only purpose of this sight is to facilitate aiming by using a virtual illuminated aim (reticle). It is understood that this sight is suitable for aiming only at those objects which are visible with a naked eye and therefore is unsuitable for aiming at remote and poorly visible targets, e.g., dusk or at night time. Another drawback of the sights with an illuminated or virtual sight is inaccuracy of aiming caused by parallax. Parallax is the apparent displacement of an observed object (target), which occurs when the viewer changes his/her position with respect to this object. Parallax is inevitable because in each aiming the viewer""s eye assumes different position with respect to the sight. The closer the virtual sight (reticle) to the viewer""s eye, the greater is the parallax. That is why rifles allow better aiming and shooting accuracy than guns, which have barrels much shorter than barrels of the guns and therefore closer position of the sight to the viewer than the sight of the rifle.
It is an object of the present invention to provide an optical sight which is simple in construction, inexpensive to manufacture, small in size, suitable for aiming at targets in a wide range of shooting distances without time-consuming replacements or refocusing of optical elements of the sight, suitable for use under combat conditions, does not require substantial reconstruction of an existing telescopic optical sight, can be attached to any existing telescopic sight with simple modification, and, in certain embodiments, suppresses effect of parallax. Another object of the invention is to provide a method of bore-sighting of the sight of the present invention aimed at improvement in the accuracy of shooting.
An optical sight system of the invention with a wide range of shooting distances comprises a combination of a telescopic optical sight with a reticle type sight. In the context of the present invention, the term xe2x80x9creticle-type sightxe2x80x9d or xe2x80x9creticle sightxe2x80x9d covers any illuminated or non-illuminated reticle for use separately from the telescopic sight with which the aforementioned reticle sight is combined. More specifically, a telescopic optical sight intended for aiming at distant targets has an objective lens assembly on one end and an eyepiece lens assembly on the opposite end. The objective lens assembly and the eyepiece lens assembly are located on a common optical path. Installed on the outer side of the telescopic optical sight is a conventional reticle sight intended for aiming at short distances. The reticle sight consists of a partially transparent mirror attached to the outer surface of the telescopic sight at the distal end of the telescopic sight. The telescopic sight supports on its outer surface a light source, which emits a light beam onto the aforementioned partially transparent mirror. The mirror reflects a part of the beam incident on its surface toward a full-reflection mirror attached to the outer surface on the proximal end of the telescopic tube. This mirror is interlocked with the second full-reflection mirror so that when the first full-reflection mirror receives the beam reflected from the semitransparent mirror and carrying the image of the reticle, the second full-reflection mirror closes the eyepiece lens assembly of the telescopic sight and at the same time reflects the image of the target and of the reticle imposed thereupon to the viewer""s eye. When it is necessary to use the telescopic sight for aiming at a distant target, the first full-reflection mirror is turned away from the path of the aforementioned beam that carried images of the target and of the reticle, whereas the second full-reflection mirror, which is interlocked with the first one, uncovers the eyepiece lens assembly of the telescopic sight and thus allows the viewer to see the image of the target only through the telescopic sight. As a result, a viewer either can see the target and image of the reticle only through the reticle sight or can see the target only through the telescopic sight.